Scientific Forecaster Discussion
fxus65 kslc 192159
Area forecast discussion
National Weather Service Salt Lake City Utah
359 PM MDT Thu Oct 19 2017
Synopsis...a cold storm system will move across the area Friday
into Saturday. Ridging will build in for Sunday through the
middle of next week.
Short term...weak trough slowly moving northeast across central
and southern Utah this afternoon and will continue to bring the
potential for a few showers into this evening. As this system
exits tonight a stronger and colder system will come in across the
northern Great Basin. The brunt of the system will impact northern
half of the County Warning Area with rain in the valleys and snow above about
6500-7000 ft with a few inches of accumulation. The associated
cold front will move into the northwest corner of Utah about daybreak and
to the central Wasatch front by about noon or shortly before.
Prefrontal southerly winds will keep temperatures quite mild along
the Wasatch front tonight with readings generally in the 50s
except 40s in the protected areas. Strong west to northwest winds
are expected across the northwest desert behind the cold front
with gusts over 45 mph possible for a few hours. The midnight crew
may want to consider a Wind Advisory if models continue to show
somewhat stronger 700mb winds. The 18z GFS is now showing 50 kts
at 700mb near Wendover at 18z.
Farther south the strongest winds will be pre-frontal across south
central Utah. Winds across Lake Powell region and canyonlands
could gust above 40-45 mph. Once the front GOES through late
afternoon the winds will shift to the west and gradually subside
in the evening. A few showers should reach as far south as
Beaver County and the southern mountains but the front overall
will be dry across most of the south.
Temperatures will be as much as 20 degrees colder across the north
Saturday than they are today and about 10 degrees colder across
the south. As the ridge begins to build in later Saturday the
700mb warm advection will spread clouds across northern Utah and
southwest Wyoming. However, moisture looks minimal and most
likely will remain north of the Idaho-Utah border.
Long term (after 12z sun)...the warm front at the nose of the
short wave ridge building into the Great Basin will be moving out
of nrn Utah Sun morning. Clouds across the north will be dissipating
and the airmass warming during the day with surface temps
responding well due to a well mixed airmass. Models now produce a
little qpf for the far nrn mtns Sun morning and added some low
pops for this area.
The ridge remains centered to our west thru Mon with another weak
flat wave on the NW flow bringing clouds and wind to the nrn County Warning Area
Sun night into Mon. Do not expect any precip from this but it should
prevent valley inversions from developing and expect highs Mon to
be quite mild once again.
The strong upper ridge moves overhead Mon night thru Tue night
with a very mild airmass aloft. Increasing inversions however may
result in temps not warming much more in the nrn and ern valleys.
The guidance agrees that the ridge retreats west somewhat Wed into
Thu as a low amplitude but vigorous short wave trof clips the nrn
County Warning Area. Do not expect precip from this feature either but once again
it should bring some cloudiness, and increase in winds, and
cooling aloft to the area.
Aviation...northwest winds are expected to prevail at kslc through
02z before switching back to the south. There is a 30 percent
chance these winds become southerly before 02z. South winds are
expected to become gusty after 06z, with gusts in excess of 25 kts
likely overnight through Friday morning. VFR conditions will prevail
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